Field of the Invention
The present invention relates to polypeptides having protease activity, and polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of using the polypeptides in beer production.
Description of the Related Art
The present invention provides polypeptides having protease activity and polynucleotides encoding the polypeptides.
The present invention also provides methods of improving colloidal stability in a beverage using the polypeptides of the invention.
Many beverages like beer, wine, juice etc. develop precipitates during manufacture or upon storage. This phenomenon is described as haze formation. One form of haze formation is generally believed to be due to interaction of proteins and polyphenols present in the beverage. This interaction leads to the formation of insoluble or semi-soluble suspension of colloidal particles. Since haze formation may resemble cloudiness produced by microbial contamination, it is generally preferred that the beverages, particularly beer, are very clear and transparent even upon long storage. Hence processes have been developed to reduce such haze formation. These processes target either the proteins or the polyphenols or both.
Silica gels, Bentonite, Poly(VinylPolyPyrrolidone) (PVPP) etc. have been used to adsorb proteins and polyphenols, decreasing haze formation and improving colloidal stability. However, such materials, when used repeatedly result in diminishing returns and consequently lead to increased costs. Moreover, they also remove other desirable compounds from the beverage, which may affect its quality.
Enzymes, particularly proteases, are also used during fermentation to improve the colloidal stability of beverages, particularly beer. Traditionally, proteases like papain and bromelain have been used to reduce chill haze formation. However, these proteases have been shown to affect the foam stability of the beverage by hydrolysing the proteins that are involved in formation and stabilization of foam. Moreover, these also cause flavour changes in the beverage. Another approach has been the use of proteases that hydrolyse mostly the haze forming proteins and rarely the foam forming proteins. For example, a prolyl specific endoprotease is known (e.g., from EP 1326957).